title: Molecular breath-gas analysis by online mass spectrometry in mechanically ventilated patients: a new software-based method of CO(2)-controlled alveolar gas monitoring.
abstract: Analysis of volatile organic compounds (VOCs) in exhaled breath offers diagnostic potential in research and clinical medicine. Mass spectrometry of expiratory air allows VOC measurements in a concentration range from parts per trillion to parts per million. For the reduction of dilution-related measurement errors due to dead space admixture, the precise identification of the end-expiratory phase of expiration is essential. We used a combination of two integrated MS systems consisting of a conventional MS capable of fast CO(2) tracing controlling a second, highly sensitive MS for the measurement of VOCs based on ion-molecule-reaction-MS (IMR-MS). This study intended to test the applicability of a software-based method of CO(2)-controlled alveolar breath-gas sampling in 12 ventilated patients using acetaldehyde, acetone, ethanol and isoprene as target VOCs (IMR-MS compound integration time 500 ms, cycle time 2 ms, measurement time 120 min). CO(2)-controlled versus mixed inspiratory/expiratory results are as follows: acetaldehyde 71* (61-133) versus 63 (47-87); acetone 544* (208-1174) versus 504 (152-950); ethanol 133 (99-166) versus 123 (108-185); isoprene 118* (69-253) versus 58 (44-112) (values in ppbv as medians with 25-75%; *p < 0.05 versus mixed inspiratory/expiratory values). The applied software-based CO(2)-controlled sampling method of expiratory air resulted in significant higher concentrations of acetaldehyde, acetone and isoprene.
authors.affiliation: Department of Anesthesiology, Ludwig-Maximilians-University of Munich, Hospital Großhadern, Marchioninistr. 15, 81377 München, Germany.
authors.forename: M E
authors.initials: ME
authors.lastname: Dolch
authors.forename: L
authors.initials: L
authors.lastname: Frey
authors.forename: C
authors.initials: C
authors.lastname: Hornuss
authors.forename: M
authors.initials: M
authors.lastname: Schmoelz
authors.forename: S
authors.initials: S
authors.lastname: Praun
authors.forename: J
authors.initials: J
authors.lastname: Villinger
authors.forename: G
authors.initials: G
authors.lastname: Schelling